"The 5-minute listing filter: first-pass deal screening"

Screening and underwriting are two different jobs

Underwriting is the careful, line-by-line pro forma: rent, vacancy, taxes, insurance, management, maintenance, reserves, debt service, all the way down to a cash flow figure and the return metrics. It deserves real time and real inputs.

Screening comes before that. Its only job is to protect your underwriting time. You can't afford to spend 30 minutes proving a property is bad. You want to spend 30 seconds suspecting it, then move on to the next alert.

When you treat screening as its own deliberate step, two things change. You actually look at every alert, because looking is cheap now. And the properties that reach your spreadsheet are already halfway decent, so the careful work feels worth doing.

Check 1: obvious disqualifiers (30 seconds)

Start with the checks that need no math. Some properties are a no on sight, and you want to catch those before you spend any arithmetic on them.

Scan the listing for:

• A location you would never actually operate in. Too far to manage, a submarket you don't know, an area you've already ruled out.
• A property type outside your strategy. If you buy small multifamily, a rural land listing isn't a deal you missed. It's noise.
• HOA fees heavy enough to sink the math before you start. A few hundred dollars a month in HOA dues changes every number downstream.
• Red flags in the photos and the description. "Cash only," "investor special," "sold as-is," boarded windows, or a description that talks about everything except the house. These don't always kill a deal, but they tell you the property needs a heavier rehab analysis than a 5-minute screen can give. If you don't do heavy rehab, that's a disqualifier for you.

Disqualifiers are personal. Your list depends on your strategy and your market. Write yours down once, and the 30-second scan becomes automatic.

A listing that clears this moves on to the math.

Check 2: the rent-to-price ratio

The fastest useful number in real estate is the ratio between monthly rent and purchase price.

rent-to-price ratio = monthly rent ÷ purchase price

The old shorthand for this is the 1% rule: a rental's monthly rent should land near or above 1% of its price. Treat the 1% figure as a marker, not a law. In expensive markets a working screen might use a lower bar. The point of the check isn't the exact percentage. It's that you have a consistent line, and listings that fall well below it get dropped without a second look.

If the listing doesn't post a rent figure, estimate one in your head from what you know the area rents for. A screen tolerates a rough rent number. Underwriting later will not.

Illustrative example. A house listed at $150,000 with expected rent of $1,650 a month. $1,650 ÷ $150,000 = 0.011, or 1.1%. That clears a 1% bar with a little room. Keep going.

A listing that comes in far under your line, say 0.6%, almost never recovers in the later checks. Drop it now and save the arithmetic.

Check 3: the rough cash flow gut check

A property can clear the rent-to-price ratio and still lose money every month once the mortgage is in. The third check is a back-of-envelope test for whether positive cash flow is even plausible.

Use the 50% rule. It's a rule of thumb that says a rental's operating expenses, meaning taxes, insurance, maintenance, management, vacancy, and reserves, but not the mortgage, tend to run around half of the gross rent over time. It's rough. It's also good enough for a screen.

So take half the monthly rent and set it aside for expenses. What's left is the money available to cover the mortgage payment and, you hope, leave something over.

rough money for debt + cash flow = monthly rent × 0.5

Then compare that to a ballpark mortgage payment. You don't need a precise figure here. Use a payment estimate at whatever rate you'd actually be quoted, on whatever down payment you actually use. If half the rent comfortably clears that payment, the property is worth a full underwrite. If half the rent barely covers the payment, or doesn't cover it, the deal is thin or negative, and the screen has done its job.

Illustrative example, continued. The same $150,000 house renting for $1,650. Half of $1,650 is $825 set aside for expenses, which leaves $825 to cover debt service. Say a mortgage payment on this property works out to roughly $700 a month with the financing you'd use. $825 − $700 = $125 a month of rough cushion. That's positive, but thin enough that you'd want the real numbers before deciding anything. It clears the screen. It earns a full underwrite.

The 50% rule will be wrong for any specific property. A new roof, a low-tax area, and self-management push expenses below 50%. An old building and a high-tax area push them above. Screening doesn't need precision. It needs to catch the property whose numbers can't work even on generous assumptions.

A listing that fails, start to finish

Illustrative example. A listing at $320,000 with expected rent of $1,900 a month. It clears the disqualifier scan: right area, right property type, no HOA, clean photos. Then the ratio: $1,900 ÷ $320,000 = 0.0059, or about 0.59%. That's well under a 1% bar, and not close. There's no reason to run the cash flow check. Half of $1,900 is $950 against a mortgage on a $320,000 purchase, and that math doesn't survive. Drop it. Total time spent: under a minute.

That listing might be a fine house. It might suit an owner-occupant well. As a rental screened for cash flow, it's a no, and you found that out in under a minute instead of after 30.

What the filter won't do

A property that passes all three checks is not a good deal yet. It's a property worth studying. Every listing that clears the filter still needs a full, careful underwrite before it's worth an offer: real rent comps, real expense numbers, real financing terms. The screen earns a property the right to your time, and nothing more.

The filter also won't catch everything. A property can pass all three checks and still fall apart under real numbers. A tax bill higher than the 50% rule assumed. A rent estimate that was optimistic. A roof at the end of its life. That's expected. A screen is built to be fast, not exact, and its job is to make sure the 2 or 3 listings that reach your spreadsheet each week are worth the spreadsheet.

Putting it to work

Run the filter the next time your alerts come in. Disqualifiers first, then the rent-to-price ratio, then the rough cash flow check. Most listings will fail one of the three in well under 5 minutes, and you'll drop them and feel fine about it. The few that pass are your real work for the week.

Real estate investing carries risk, including the risk of losing money, and a screening framework doesn't change that. It decides what you study, not what you buy. Do your own full diligence on anything that clears the filter, and get qualified advice where you need it.

This screening pass is the workflow Whoof is built around. Whoof automates the first-pass screening of new listings, so the properties that reach you have already cleared the kind of checks above. If turning a flood of listing alerts into a short list of worth-a-look properties is the part that eats your time, that's the problem Whoof is built to handle.